Systèmes d'adaptation des bactéries

Adaptation systems of bacteria

Atelier Master 2 MIF (Microbiologie Intégrative et Fondamentale)

Role of sigma factors in regulation of gene expression in bacteria.

Cécile Jourlin-Castelli and Aurélia Battesti

In prokaryotes, transcription initiation is a crucial step of gene expression. Sigma factors are key players in this process: they associate with the catalytic core RNA polymerase allowing it to ensure the essential steps of initiation: promoter recognition and opening, and synthesis of the first few nucleotides of the transcript. In addition to the housekeeping sigma factor (σ70), several alternative factors allow the organisms to adapt to changes in physiological and environmental conditions. The expression and the activity of these alternative sigma factors are submitted to regulation through diverse mechanisms. The aim of this workshop is to survey some of them and to highlight the diversity of the strategies that prokaryotes have evolved to program the RNA polymerase in order to regulate key processes such as: morphogenesis, motility, adaptation, virulence…

Repliement, protection et dégradation des protéines, rôle des protéines chaperons.

Olivier Genest, Marianne Ilbert, Chantal Iobbi-Nivol

  Pour acquérir leurs fonctions cellulaires, les protéines doivent se replier correctement pour obtenir une structure tridimensionnelle dite native. Cependant, le repliement des protéines est rarement spontané dans l’environnement cellulaire rempli de macromolécules biologiques et sujet aux stress environnementaux. L’obtention d’une protéine active nécessite donc des mécanismes fins de repliement et d’assemblage qui font généralement intervenir des protéines « chaperons ». Ces protéines chaperons permettent non seulement le repliement mais également la protection, l’activation, la désagrégation et la dégradation de protéines cibles. Elles jouent un rôle essentiel pour maintenir l’homéostasie protéique cellulaire (protéostasie). A travers l’analyse de publications scientifiques, nous aborderons l’implication de protéines chaperons, essentiellement bactériennes, dans le maintien de l’intégrité cellulaire. Nous découvrirons ainsi la diversité de fonctions et de mécanismes d’action de ces protéines.

  In every cells, proteins have to acquire their native conformation to get their physiological function. However, the folding process is generally not spontaneous in vivo due to the high concentration of macromolecules inside the cell and also due to the many stress conditions the organisms have to face. That is why chaperone proteins are present in all living organisms and are essential to maintain protein homeostasis (also called proteostasis) in the cell. Chaperones are involved at almost every steps in the protein folding process. In particular, they allow the protection, folding, activation, disaggregation, and degradation of the other proteins. During our course, we will talk about several classes of chaperones to get an overview of the high diversity of functions and of the molecular mechanisms of these fabulous proteins. By analyzing scientific publications, we will focus on the chaperones present in bacteria.